title: Mechanism of L-leucyl-L-leucine methyl ester-mediated killing of cytotoxic lymphocytes: dependence on a lysosomal thiol protease, dipeptidyl peptidase I, that is enriched in these cells.
abstract: Exposure of murine or human lymphocytes to L-leucyl-L-leucine methyl ester (Leu-Leu-OMe) results in selective killing of cytotoxic lymphocytes, whereas helper T cells and B cells remain functionally intact. Cytolytic lymphocytes incubated in the presence of toxic concentrations of Leu-Leu-OMe were found to contain membranolytic metabolites of the structure (Leu-Leu)n-OMe, where n greater than or equal to 3. The sensitivity of cytotoxic lymphocytes to Leu-Leu-OMe was found to be dependent upon production of these metabolites by a lysosomal thiol protease, dipeptidyl peptidase I, which is present at far higher levels in cytotoxic lymphocytes than in cells without cytolytic potential or not of bone marrow origin. Thus, this granule enzyme is required for the unique effects of Leu-Leu-OMe and may provide a target for the development of other immunotherapeutic agents designed to delete cytotoxic lymphocyte responses.
authors.affiliation: Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235.
authors.forename: D L
authors.initials: DL
authors.lastname: Thiele
authors.forename: P E
authors.initials: PE
authors.lastname: Lipsky
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D020789:Cathepsin C; D003513:Cycloheximide / Q000494:pharmacology; D003602:Cytotoxicity, Immunologic / Q000187:drug effects*; D004151:Dipeptides / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology*; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007460:Iodoacetamide / Q000494:pharmacology; D008247:Lysosomes / Q000201:enzymology*; D011480:Protease Inhibitors / Q000494:pharmacology; D013602:T-Lymphocytes, Cytotoxic / Q000166:cytology* / Q000187:drug effects / Q000201:enzymology
chemical_list: D004151:Dipeptides; D011480:Protease Inhibitors; D000643:Ammonium Chloride; C045139:leucyl-leucine-methyl ester; D003513:Cycloheximide; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases; D020789:Cathepsin C; D007460:Iodoacetamide